Previously available foldable multi-sectioned agricultural implements include a main frame and two or more wing frames hinged to the ends of the main frame. A rockshaft with a pair of parallel connected lift cylinders constrained for operation in unison by the rockshaft raise and lower ground engaging wheels on the main frame. Each of the wing frames includes a lift cylinder connected in series with one of the parallel connected cylinders so that the implement raises and lowers in generally level fashion. Often, a single point depth control having a valve connected to the hydraulic circuit provides an adjustable depth stop function on lowering of the implement. Lift wheels on the wing frames have to be moved to specific locations for implement folding to avoid unwanted contact with tools or frame members.
Rockshafts are heavy, expensive and cumbersome, and rockshaft windup results in uneven depth control. Recent implements have featured individually controlled lift wheel arms on the main frame without a rockshaft connecting adjacent arms. However, without a rockshaft, synchronization of the cylinders on the main frame with those on the wing frames is difficult. Providing a hydraulic lift system wherein the lift cylinders operate in unison across the entire width of the machine as the implement raises and lowers level continues to be a problem. Uneven loading on the implement frame causes differential extension and retraction of parallel connected cylinders. Although sophisticated cylinder control systems such as shown in commonly assigned U.S. Pat. No. 5,957,218 are available and work well for lift systems without rockshafts, some operators still prefer simpler conventional and less expensive hydraulic systems. Further, providing desired wheel tuck features for folding of the machine for transport and unfolding of the machine for field operations without wheel interference often requires expensive and complicated hydraulic circuitry.